This invention relates generally to diagnostic tools for diagnosis of motor vehicle engines. More particularly, the invention relates to a diagnostic tool for diagnosing both electric-operated fuel injectors of an engine and the driver circuits that operate the fuel injectors.
Certain motor vehicle engines have fuel injectors that inject fuel into the engine cylinders where the injected fuel forms a portion of a combustible mixture that is ignited to power the engine. Certain fuel injectors are electrically operated by a control that includes driver circuits through which electric current is delivered to operate the fuel injectors. In a diesel engine there is typically one fuel injector per cylinder. Each injector injects fuel directly into the respective cylinder at a proper time in the engine cycle.
When an engine fuel injection system is being serviced or diagnosed, an ability to test each individual fuel injector and its respective driver circuit may be useful. However, such comprehensive testing of certain engines may be difficult and/or inconvenient for one or more different reasons, such as accessing individual fuel injectors in an engine compartment and the individual driver circuits. Comprehensive testing often includes the need to connect various pieces of test equipment, like current probes, voltmeters, oscilloscopes, etc., to the engine electrical system that serves the fuel injectors. Making the proper connections of such equipment to various portions of the engine electrical system may require a significant amount of time because of difficulty and inconvenience in obtaining the desired access.
The present invention relates to a diagnostic tool for facilitating diagnostic testing of an engine fuel injection system by providing convenience in connecting certain pieces of test equipment to a portion of the engine electrical system that pertains to the fuel injectors and their driver circuits. The diagnostic tool itself contains certain test equipment, such as indicator lights, that is useful in diagnosis of the fuel injectors and their driver circuits.
A preferred embodiment of the inventive diagnostic tool comprises a portable enclosure that can be carried by hand. This enables the tool to be conveniently moved about in a service facility to diagnose a motor vehicle that has been brought into the facility for service. The tool has a front face containing various switches and indicator lights and indicia for correlating switch positions and indicator lights with particular fuel injectors and driver circuits. The tool also has various ports for establishing connection of various pieces of test equipment, like some of those mentioned above, with the engine electrical system. Two of the ports comprise multi-terminal connectors that enable the tool, in effect, to be transparently inserted between the driver circuits and the fuel injectors.
The tool insertion is accomplished by disconnecting mated multi-terminal connectors in the vehicle, connecting one of the disconnected connectors through one jumper wiring harness to one of the multi-terminal connectors of the tool, and connecting the other disconnected connector through another jumper wiring harness to the other multi-terminal connector of the tool. The use of jumper harnesses allows the tool to be placed in a convenient location remote from the engine where it can be readily observed and easily operated by service personnel. By providing separate jumper harnesses that can be connected to and disconnected from the tool, rather than harnesses that are permanently connected to the tool, it becomes possible for one tool to service vehicles whose electrical wiring between the fuel injectors and their driver circuits has different pin-outs in the mated connectors. Any particular pair of jumpers is configured to establish proper circuit connection of a particular pin-out of the particular vehicle connectors to the tool connectors.
It is believed that the diagnostic tool of the invention provides an effective solution for facilitating various aspects of fuel injection system diagnosis.
One general aspect of the invention relates to a diagnostic tool for testing fuel injectors and their driver circuits in a fuel injection system of an engine in a motor vehicle. The tool comprises a driver-connection port for connection to the driver circuits and an injector-connection port for connection to the fuel injectors. A load simulates that imposed by a fuel injector on a driver circuit. Individual position selector switches, each of which is individual to a particular fuel injector and the respective driver circuit, is selectively operable to first and second positions. In its first position, the position selector switch connects the simulated load through the driver-connection port to the respective driver circuit when the driver circuits have been disconnected in the vehicle from the fuel injectors and instead connected to the driver-connection port. In its second position, the position selector switch connects the respective driver circuit through the tool with the respective fuel injector when the driver circuits and the fuel injectors have been disconnected in the vehicle from each other, the driver circuits are instead connected to the driver-connection port, and the fuel injectors are instead connected to the injector-connection port.
Another general aspect of the invention relates to a diagnostic tool for testing a fuel injector and a respective driver circuit in a fuel injection system of an engine in a motor vehicle when the driver circuit and the fuel injector have been disconnected from each other in the vehicle and instead connected to the tool. The tool comprises a driver-connection port for connection of the driver circuit to the tool, an injector-connection port for connection of the fuel injector to the tool, and an electric current path through the tool for conducting electric current from the driver circuit to the fuel injector. A sensor senses magnetic flux created by flow of electric current through the current path and illuminates an indicator when the magnetic flux sensed by the sensor is indicative of the delivery of a particular electric current from the driver circuit to the fuel injector.
The sensor comprises an electronic circuit chip disposed proximate at least one turn of a conductor of the current path that effectively amplifies the density of magnetic flux that results from the flow of electric current through the current path, and the indicator comprises a light-emitting diode that is operated by the chip to illuminate when the magnetic flux acting on the sensor exceeds an amount that indicates the particular electric current flow from the driver circuit to the fuel injector.
Still another general aspect of the invention relates to a diagnostic tool for testing fuel injectors and driver circuits that operate the fuel injectors in a fuel injection system of an engine in a motor vehicle when the driver circuits and the fuel injectors have been disconnected from each other in the vehicle and instead connected to the tool. The comprises a driver-connection port for connection of the driver circuits to the tool, an injector-connection port for connection of the fuel injectors to the tool, and a respective electromagnetic sensor for sensing flow of electric current from each driver circuit through the tool to a respective fuel injector. The tool also has a first auxiliary-equipment-connection port for connecting an oscilloscope to the tool, an injector-selector switch for selectively connecting the electromagnetic sensors to the first auxiliary-equipment-connection port, a second auxiliary-equipment-connection port for connecting an oscilloscope to the tool, and an electromagnetic sensor connected to the second auxiliary-equipment-connection port for sensing flow of electric currents from multiple ones of the driver circuits to their respective fuel injectors.
Still another general aspect of the invention relates to a diagnostic tool for cylinder contribution testing of fuel injectors and their driver circuits in a fuel injection system of an engine in a motor vehicle when the driver circuits and the fuel injectors have been disconnected from each other in the vehicle and instead connected to the tool wherein the tool comprises a driver-connection port for connection of the driver circuits to the tool, an injector-connection port for connection of the fuel injectors to the tool, and switches that allow the driver circuits to be individually selectively connected and disconnected, through the tool, to and from the fuel injectors.
Another general aspect of the invention relates to a diagnostic tool for testing fuel injectors and their driver circuits in a fuel injection system of an engine in a motor vehicle when the driver circuits and the fuel injectors have been disconnected from each other in the vehicle and instead connected to the tool. The tool comprises a driver-connection port for connection of the driver circuits to the tool, an injector-connection port for connection of the fuel injectors to the tool, auxiliary-equipment-connection ports that allow connection of auxiliary test equipment to the tool, a load that simulates the load imposed by a fuel injector on a driver circuit, multiple indicators, and switches.
The switches allow the driver circuits to be selectively connected and disconnected, through the tool, to and from the fuel injectors. When disconnecting a driver circuit from a respective fuel injector, the switches connect that driver circuit to the simulated load to enable a driver circuit test to be performed with the result being indicated by one of the indicators. When disconnecting a driver circuit from a respective fuel injector, the switches connect a fuel injector to one of the auxiliary-equipment-connection ports to enable a fuel injector test to be performed via a piece of test equipment connected to that one auxiliary-equipment-connection ports. When connecting a driver circuit to a respective fuel injector, the switches enable a driver-injector test to be performed with the result being indicated by a respective indicator, and with a waveform of electric current flow from the driver circuit to the fuel injector being made available to another piece of test equipment connected to another of the auxiliary-equipment-connection ports.
Still another general aspect of the invention relates to a method for conducting diagnostic testing of fuel injectors and their driver circuits in a fuel injection system of an engine in a motor vehicle. The method comprises disconnecting mated connections between the driver circuits and the fuel injectors, connecting the driver circuits to a driver-connection port of the tool, connecting the fuel injectors to an injector-connection port of the tool, and then conducting at least one of three tests.
A fuel injector test, by connecting a piece of test equipment that measures an electrical characteristic of an electric actuator of a fuel injector to an auxiliary-equipment-connection port of the tool, and operating switches of the tool to disconnect the actuator of the fuel injector from the respective driver circuit and to instead connect the actuator to the auxiliary-equipment-connection port.
A driver-injector test, by connecting an oscilloscope to an additional auxiliary-equipment-connection port of the tool, and operating the switches of the tool to connect the fuel injector actuator to the respective driver circuit and to connect to the additional auxiliary-equipment-connection port, a sensor that senses the electric current flow from the respective driver circuit to the fuel injector actuator.
A driver circuit test, by operating the switches of the tool to disconnect the actuator of the fuel injector from the respective driver circuit and to instead connect the respective driver circuit to a load that simulates the load imposed by the respective fuel injector.
A cylinder contribution test, by operating the switches of the tool to connect each fuel injector actuator to its respective driver circuit, and then selectively operating the switches to selectively disconnect certain fuel injector actuators from their driver circuits while leaving the remaining fuel injector actuators connected to their driver circuits.
Diagnostic testing of electrical circuits in an engine fuel injection system can check both circuit devices and wiring connected with those devices.
The foregoing, along with further aspects, features, and advantages of the invention, will be seen in the following disclosure of a presently preferred embodiment of the invention depicting the best mode contemplated at this time for carrying out the invention. The disclosure includes drawings, briefly described as follows.